DURATION = 9 * 60 # minutes
class Person
  @@population = []
  attr_reader :use_duration
  attr_accessor :frequency

  def initialize(frequency = 4, use_duration = 1)
    @frequency = frequency
    @use_duration = use_duration
  end

  def self.population
    @@population
  end

  def need_to_go?
    rand(DURATION) + 1 <= @frequency
  end
end